with mitt romney getting a bite to eat in denver. and president obama visiting the hoover dam for the first time. both have relied heavily on their running mates this week to lead their campaigns. >> how they can justify raising taxes on the middle-class has been varied the last four years. >> reporter: it didn't take long for paul ryan to pounce on that comment. >> vice president biden just today said that the middle-class, over the last four years has been, quote, buried. we agree. that means, we need to stop digging by electing mitt romney. >> reporter: the latest abc news/"washington post" poll shows the race for president is still very close, which means every word and gesture tonight could impact the election. brandi hitt, abc news, denver. >> thanks to brandi hitt. abc's coverage of tonight's debate begins at 9:00 eastern, 6:00 pacific. >>> now, we turn to the trouble at american airlines. and actually progress on two fronts this morning. there is new movement in the bitter labor dispute between the airline and its pilots unio